A. aurita has a number of predators including other Cnidarians, Gastropods and fish. Specifically Cyanea capellata is a species of Cnidaria known to prey upon A. aurita. A. aurita is highly susceptible to C. capillata and if contact occurs there is an increase in swimming frequency and scarring to the bell (Hansson & Kultima 1995). Another predator is Drymonema larsoni, a most effective A. aurita predator essential in controlling A. aurita blooms by reducing and halting the growing population. When left unchecked, A. aurita will rapidly multiply and cause a collapse of lower trophic levels (Bayha et al. 2012). Other known predators include nudibranchs and zooplanktivorous fish (Aria 1997), and anthropological effects such as pollution and habitat destruction.

The most common location of A. aurita is the Adriatic Sea. No matter the density this species plays key roles in the planktonic ecosystems, increasing the carbon biomass in the ocean, controlling the mesozooplankton abundance via predation pressure, and regenerating nutrients within the ecosystem to improve phytoplankton primary production (Shimauchi & Uye 2007).

When aggregation events occur and therefore blooms, downstream trophic cascades are caused (Moller, Riisgard 2007). The large numbers in the summer months regulate the pelagic structure of ecosystems (Ishii & Tanaka 2001) and therefore control prey populations through a stronger than usual predation impact (Moller, Riisgard 2007). Blooms within the Adriatic Sea can affect humans, ecosystem, fisheries and machinery. Clearing pumps, pipes, water intakes etc of thousands of jellies is a costly and time-consuming process and most often there is insufficient information available to understand the cause of the bloom, or how to prevent recurrence.

The aggregation of animals may be caused by a variety of factors, but most recent outbreaks are believed to be due to temperature change. Ocean temperatures are increasing and anthropogenic run off provides an abundance of nutrients for A. aurita's  food source, zooplankton.

Also, an increase in the number of sites available for larval settlement due to marine construction (habitat loss) causes blooms. As does a decrease in the number of natural A. aurita predators, zooplanktivorous fish. Zooplanktivorous fish populations are increasing due to changes in fisheries (Melica, Invernizzi & Caristi 2014). For example, if higher order fishes such as piscivores (fish eating fishes) are harvested then zooplanktivorous fishes overpopulate.

The medusa form of A.aurita has an unusual relationship with two fish species. The relationship with Chloroscombrus chrysurus is commensal, the fish benefits from protection and food provided by the medusa, but A. aurita acquires safe habitat, no benefit as such but also no negative. This relationship is dependent on the stage of development of both partners as only the small juvenile fish are found living with the adult A. aurita. (Aria 1997).

A. aurita also has a commensal relationship with the fish species Trachurusjaponicas. Research by Masuda 2009 found that the juvenile fish were only associated with the A. aurita when in the presence of a predator and in darkness, but was dependent on the age and size of the fish. There were a number of reasons for this association; school formation, hiding and food. When there is high predation pressure A. aurita may also function as a transportation vehicle for the fish species (Masuda 2009). 

The A. aurita has a life cycle with two adult morphological and physiological identities. The animal is able to transition from one morph to the next and back and forth between stages. The machinery responsible for the transition between the two is activated when the appropriate stimuli are available. Triggers are environmental or seasonal and are based on a temperature shift from 18^oC-10^oC (Fuchs et al. 2014).

As well as strobilation the A. aurita like other Cnidarians have the ability to asexually regenerate after significant injury via fragmentation (Rupert, Fox & Barnes 2004).  Sexual reproduction of the A. aurita occurs in the medusa morph. The medusae of A. aurita are gonochoristic sexually reproducing individuals. The germ cells are kept within the gonads of each gastric pouch which are within the coelenteron walls. The oocytes produced are round in shape and approximately 90 micrometres in diameter and covered in microvilli. The male medusae release sperm from the ends their oral arms in strands of mucus that are picked up by the females oral arms and broken apart. Sperm is then transported into the female’s gastrovascular cavity where fertilisation occurs.

Zygotes exit through the mouth and are recaptured by the oral arms and transferred into brood pits. After cleavage and gastrulation, the embryo elongates and forms into a planula or lecithotrophic larva. Once mature they are released from the brood pits into the water column, in search of favourable environmental conditions to settle and morph into a polyp. (refer to Development and Settlement section and Figure 3)

The polyp of A.aurita is funnel shape with a wide oral end and thin aboral attachment site. The A. aurita polyp is small and only reaches a few centimetres in height and a maximum of 2mm in diameter (Rupert, Fox & Barnes 2004).  The polyp form is able to undergo clonal reproduction via transverse and longitudinal fission, budding and fragmentation. The transition from polyp to medusa consists of three phases.

The first is metamorphosis, second strobilation and finally morphogenesis. Polydisk strobilation is a segmentation process which occurs via transverse fission that begins at the apical end of the polyp and progresses toward the alternate end.The resulting stack of multiple disk-like segments detaches from the polyp and enters the water column as ephyra. The ephyra independently begin a planktoniclife, which take three months to reach adult medusa sexual maturity (Fuchs etal. 2014; Rupert, Fox & Barnes 2004). (Figure 3)

The resulting sexually produced zygote of A. aurita within the oral arm brood pits undergoes holoblastic equal cleavage, from which a coeloblastula is the result. During cleavage the blastomeres remain closely connected. Gastrulation occurs via multiple points of invagination of the embryo wall at the animal pole and the embryonic wall becomes ciliated. The blastopore consists mainly of yolkgranules which give rise to the mouth/anus and the blastula walls are made from narrow, high cells. The blastocoel is small and after gastrulation becomes the mesoglea (Mayorova, Kosevich & Melekhova 2012; Rupert, Fox & Barnes2004).

The gastrulation process of the larvae reveals two true tissue layers, the ectoderm and endoderm which will become the epidermis and gastrodermis respectively (Rupert, Fox & Barnes 2004). The planula larvae of the A. aurita have an ectodermal nervous system made up of multiple neurons which are found at the anterior pole. This is where an apical organ holds several types of apical neurons and the lateral ectoderm holds lateral neurons.

Apical neuron axons congregate beneath the apical organ where they spread to the rest of the body. These body parts are activated throughout development and metamorphosis of the planula. The nervous systems multiple apical neurons secrete specific neuroactive chemicals at each stage of planula development (Mayorova, Kosevich & Melekhova 2012).

The settlement of the planula occurs on vertical substrate surfaces. The attachment occurs by enlarging the anterior end. Once connected with the chosen surface the body pulses causing the anterior end to widen.This ensures strong contact with the attachment site. The pulsing also causes the body of the planula to shorten until a certain point is reached and the body retracts causing the posterior end to fasten.

After further development the future mouth is present as a furrow, and tentacle buds appear. Once metamorphosis is complete the transition from a mobile planula to a sessile polyp has been completed and after maturation will undergo strobilation (Mayorova,Kosevich & Melekhova 2012).

Locomotion in the medusa form of A. aurita includes reaching food sources, escaping predation, travel and interaction during reproduction. Locomotion relies on structural support and the nervous system to generate repeated pulse cycles which dictate the animal’s movement. The bell of the body changes shape with time over the pulse phase. During the power stroke the bell diameter controlled by circular muscles is contracted and the bell height is decreased as water is forced out of the animal. During the recovery stroke the circular muscles are relaxed causing to diameter to increase as the height of the bell increases also, due to the bell filling with water (McHenry & Jed 2003; Costello & Collin 1994). The duration spent in each phases is different, the power stroke is quicker than the recovery stroke which takes more time (Costello & Colin 1994). The inset DVD shows locomotion of A. aurita (seawater aquarium, 2015).

The machinery causing pulsations drives the animal through the water. The nerve ring conducts motor impulses towards the body parts responsible for swimming/pulsating which are the ganglion, nerve rings and muscles around the subumbrella epithelial. Due to the muscles being either contracted or relaxed depending on which stroke the animal is in, the nerve impulses need to reach the muscles simultaneously. Which ensures efficiently movement through the water (Rupert, Fox & Barnes 2004).

The animals ability to move through the water depends on size, shape and its behaviour. It is unknown precisely how the A. aurita swims. Due to the oblate bell shape of A. aurita they primarily should locomote via paddling. This method decreases the overall number of pulse cycles throughout its lifetime, because paddling avoids the high costs and energy demands of active swimming/jet propulsion. Jet propulsion is more common among species with a bullet shape bell which is used to force water out and create jet propulsion and therefore thrust. There is evidence that A. aurita although lacking the specialised organ used to create the jet, are able to create vortices around their bell when pulsing which produces thrust (McHenry & Jed 2003).

As the medusa grows the expected outcome would be proportional features. But the A. aurita does not grow this way.

The species has adopted different types of swimming with alternating body sizes. Which produce different effects of acceleration, drag and thrust over an individual’s life time. The larger individuals adopt a lower pulsation rate than those of a smaller size. Therefore the smaller the individual the more frequent the pulsing. Despite this difference in pulsation frequency, larger individuals move at a quicker speed through the water over their life time than small individuals (McHenry & Jed 2003). 

The Cnidarian body has three tissue layers arranged with tetramerous symmetry. Medusa within Scyphozoa lack a velum and pharynx (Aria1997).  The outer epithelium known as the epidermis protects the organism from the surrounding environment. The second epithelium, the gastrodermis lines the gut-like multifunctional coelenteron. The gastrodermis tissue layer is responsible for connecting the epidermis and mouth on the oral side of the animal. The two epithelia layers are responsibly for Cnidocytes used in protection and defence, nerves for communication and muscles for movement.

Circulation, digestion and excretion, internal transportand reproduction are the responsibilities of the coelenteron organ within the mesoglea which is lined by gastrodermis. Radial canals extend from the coelenteron to merge with a marginal ring canal and also into each tentacle.

Between the gastrodermis and the epidermis is a thin gelatinous extracellular matrix known as the mesoglea. The mesoglea is used mainly for structural integrity and consists of fibres within a hydrated matrix (Rupert, Fox & Barnes 2004; Aria1997). 

An A. aurita polyp resembles a cylindrical column arising from an aboral holdfast with a thin mesoglea layer. The oral disk of the polyp surrounds the above manubrium,which houses the mouth at its summit facing upwards. Tentacles that surround the mouth of the animal are connected to the oral disk margin (Rupert, Fox& Barnes 2004; Aria 1997).

The medusa of the A.aurita is an oblate shape. The elongated manubrium is divided into four tentacles known as oral arms which are frilled and hang from beneath the bell. Additional, hallow marginal tentacles line the bell margin. The bell margin is arranged into a pattern of Lappets and Rhopalia. The downwards facing mouth which is found at the top of the manubrium leads to a central stomach with four gastric pouches, a reminder of tetramouse symmetry.

The gastric pouches are separated but not by septa, although the pouches have all functional organs of septa structures such as gonads, gastric filaments and septa funnels that connect each pouch.

Whereas in other Cnidarians there are usually eight paired gonads which are located in the walls of the pouches. But because the septa are absent in A. aurita there is no separation between the paired horseshoe shaped gonads, they have merged into four larger gonads which are found within the walls of the gastric pouches (Rupert, Fox &Barnes 2004). 

The medusa morph of the A. aurita species is an opportunistic tactile predator which consumes prey in the surrounding water (Rupert, Fox & Barnes 2004). On a global scale A. aurita consume a large variety of species; Copepods, fish larva, eggs, other Cnidarians, Tintinids, Gastropod larva, Polychaete larva, Rotifers and herring larva (Ishii & Tanaka 2001).

The oral arms of A. aurita create fluid motions while swimming which pull prey towards the tentacles. This mechanism may be the basis of prey selection, as the water flow created by the swimming action influences prey capture. The oral arms are laced with cnidae that wound and trap prey.This activates ingestion which causes the mouth to open. The oral arms then move towards the mouth to consume the trapped prey. Once the prey it is the coelenteron, enzyme gland cells digest the food into slurry, the paste is then circulated through the coelenteron for absorption (Costello & Colin 1994).

The inflow of water over the bell margin during the recovery phase also traps prey on the marginal tentacles. Prey that travel at a slower speed than the flow of the recovery phase will be puller over the bell and be captured on the marginal tentacles. Therefore is it expected that the larger medusa with a greater marginal force would capture larger prey,resulting in the diet of an individual changing over its lifetime (Costello& Colin 1994).

The internal cavities allows a larger surface area to collect food. Within the A. aurita threadlike gastric filaments or cirri are attached at one end to the gastrodermis allowing the other end to float throughout stomach (Rupert, Fox & Barnes 2004). Digestion in A. aurita on average takes one and a half hours if the animal has eaten its most common prey, Copepods. Ten minutes after ingestion the Copepod carapace is damaged, after thirty-five minutes the body contents leak from the exoskeleton and after forty-five minutes digestion of prey tissue is complete. This time estimate varies depending on prey size,ingestion rate and the size of the jellyfish. Other factors correlated with digestion rate are temperature bell diameter and carbon daily ration (Ishii& Tanaka 2001). 

Excretion is expelled in the form of ammonia and phosphates, which is a result of a protein rich carnivorous diet. Therefore metabolism of A. aurita is protein dominated with small amounts of carbohydrates and lipids. At higher temperatures the diet flips to more carbohydrate and lipid dominated. These excretory products after digestion are stored in the coelenteron which is flushed out regularly (Shimauchi& Uye 2007). 

The A. aurita has gas exchange surfaces on its tentacles and body wall, which are ciliated epidermal cells that circulate water and facilitate gas exchange. This water flow enters and exits after supplying the entire coelenteron with oxygen (Rupert,Fox & Barnes 2004).

Respiration of any animal will increase with the increasing in size, food availability and temperature decrease. If an A. aurita individual increases its respiration, it usually signifies growth. The extra oxygen and energy is used as additional fuel. Therefore growth requires additional energy to fuel biochemical reactions of biosynthesis, along with the energy required to maintain muscles and tissues already at the body (Moller & Riisgard 2007).

Ciliary tracts move fluid, mucus and food towards the stomach and the rest of gastrovascular system through peripheral canals. Once in the stomach there are four grooves and associated currents that move outward towards the peripheral margin through the peripheral canals.

Once the fluid reaches the periphery of the animal, it then moves inward along the peripheral grooves. Along the way ventilating the gastric pouches and cirri, gonads and the rest ofthe gastrocircular system. To maintain net movement in both directions the outward currents flow along the bottom on the grooves while the inflow currents move at the top of the grooves. Therefore separated by canals or flowing at different levels of the same structures (Rupert, Fox & Barnes 2004).

The mesoglea performs the role of the skeleton and offers buoyancy and nutrition for musculature. Connective tissue is found within the thick, gelatinous mesoglea which controls the subumbrella locomotory cross striated musculature (Rupert, Fox & Barnes 2004).

The contraction of muscles depends on the organisation of protein filaments. Scyphozoancontractile myofibrils are found within the epitheliomuscular cells. The proximal coronal muscles have circulatory orientated fibres and the radial muscles have radially orientated fibres arranged into bands. Between each radial muscle bands are septa made from a thin peri-rhopalia tissue that extends to the bell margin. There are also longitudinal myofibrils in the epidermis of the tentacles, and manubrium and oral arms (Aria 1997).

In each morph of the A. aurita there are different forms of musculature. Within the ephyra the radial swimming muscles extend beyond the coronal muscles into the lappets. Myofilaments in the ephyra are striated with interdigitated thick and thin filaments which are arranged in repeated longitudinal units. Within the polypform the coronal muscle is reduced to a narrow band and radial subumbrella muscles are found proximally. Radial muscles are found in the oral disk and longitudinal muscles are found in the epidermis of oral arms (Aria 1997).